Re: [Xen-users] dom0 freezes under high IO load

["Ulrich Windl" <ulrich.windl@xxxxxxxxxxxxxxxxxxxx>]

On 4 Mar 2007 at 15:12, bigfoot29 wrote:

> Heya. :)
> 
> Just wanted to second dom0 - crashing behavior.
> 
> Due to the fact that I have had never the same problems with 2.0.7 (and
> at least the same CPU/network utilization -> HDD-utilization should be
> compareable) I can second that with 3.0.x the behavior of dom0 got bad.
> 
> Normal uptime with 2.0.7 was up to 2 months; with 3.0.x its pending from
> 24 hours up to a week.

SLES10-x86_64:
# uptime
  8:39am  up 97 days 17:02,  1 user,  load average: 1.87, 1.83, 1.76


> 
> 2 interesting things to mention:
> 1st: When the whole system had crashed (domains also had to be started
> new) the Xen-System stays up round about a week. When I just reboot the
> server (and thus Dom0 with frozen domU's while reboot), server dies more
> often.
> 2.nd: I tried to create a simple 2 GB file using dd if=/dev/zero of...
> inside(!) a vm, and it froze the system right at the beginning of file
> creation.
> 
> All VMs are running using files as virtual harddisks; so basically it
> are no processes that do anything "special".

I'm using LVM LVs for virtual harddisks.

> 
> All running VMs are paravirtualized ones - no HVM guests.

Same here.

> 
> However, its weird that I can't use swap inside a dom0 - you can bet
> your soul on the fact that as soon as you reduce the mem (192MB maybe)
> and you have processes that want to swap out, your Dom0 WILL crash - not
> right away, but soon enough.

I can use swap in Dom0:
# free -m
             total       used       free     shared    buffers     cached
Mem:           384        380          3          0         59        154
-/+ buffers/cache:        165        218
Swap:        20481          5      20476


> 
> So basically if you want to increase Dom0 livetime, you gotta increase
> memory dedicated to dom0.

Probably there exists a critical minumum amount of RAM where Dom0 can run 
stable.

> 
> Never had THESE issues with vanilla kernels (or as mentioned the 2.0.7
> ones)
> 
> Funny thing: with a Dom0-machine just staying ready for action and
> running a samba fileserver (well, its a backup server that could run a
> VM if needed where I didn't want to put the sambaserver in a VM) I get
> the same behaviour - all 2 weeks the dom0 just gets unresponsible when
> you want to access hdd.

Why would you run a samba server in Dom0, and did you install the recent 
security 
updates for samba?

Ulrich

> 
> Please, don't start something like "well, its not supposed to run this
> or that inside a dom0" - I can't export it to a VM as long as I can't
> make sure I can access the data in the VM whenever I need them. I don't
> want to do a Backup-VM-Recovery just to recover the other vm's data...
> So for a small company you have to rely on some backup mechanisms or
> that sorta stuff. Paying 2-5000 dollar just to get a dom0 working that
> shouldn't have these child illnesses (sorry to call them that way... I
> think its just a bug that needs to be fixed)
> 
> So thats no insult on the Xen-Devs... just a plea to fix it. When I can
> help, lemme know.
> 
> 
> Regards, Bigfoot29
> 
> 
> On So, 2007-03-04 at 11:19 +0100, xen-users-request@xxxxxxxxxxxxxxxxxxx
> wrote:
> > dom0 freezes under high IO load
> 
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users



_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users